Implement MSC2174: move redacts to a content property. (#15395)

This moves `redacts` from being a top-level property to
a `content` property in a new room version.

MSC2176 (which was previously implemented) states to not
`redact` this property.

1 files changed, 7 insertions, 1 deletions

diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py
index d475fe7ae5..4501518cf0 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -326,7 +326,6 @@ class EventBase(metaclass=abc.ABCMeta):
     hashes: DictProperty[Dict[str, str]] = DictProperty("hashes")
     origin: DictProperty[str] = DictProperty("origin")
     origin_server_ts: DictProperty[int] = DictProperty("origin_server_ts")
-    redacts: DefaultDictProperty[Optional[str]] = DefaultDictProperty("redacts", None)
     room_id: DictProperty[str] = DictProperty("room_id")
     sender: DictProperty[str] = DictProperty("sender")
     # TODO state_key should be Optional[str]. This is generally asserted in Synapse
@@ -346,6 +345,13 @@ class EventBase(metaclass=abc.ABCMeta):
     def membership(self) -> str:
         return self.content["membership"]
 
+    @property
+    def redacts(self) -> Optional[str]:
+        """MSC2176 moved the redacts field into the content."""
+        if self.room_version.msc2176_redaction_rules:
+            return self.content.get("redacts")
+        return self.get("redacts")
+
     def is_state(self) -> bool:
         return self.get_state_key() is not None